Electrical switch contact structure including damping means



United States Patent ELECTRICAL SWITCH CONTACT STRUCTURE INCLUDING DAMPING MEANS William F. 'Juptner, Laguna Beach, and Gunter K. Rueb,

Laguna Hills, Calif., assignors to Babcock Electronics Corporation, Costa Mesa, Calif., a corporation of California Filed Jan. 23, 1967, Ser. No. 611,142

6 Claims. (Cl. 200166) ABSTRACT OF THE DISCLOSURE An electrical contact structure is described in which a contact member is formed with a U-shape and is provided with a damper in the form of an L-shaped leaf spring arranged between the legs of the U-shaped contact member. Relative movement between the legs of the contact member is damped by friction between a leg of the contact member and an arm of the damper.

This invention relates to improvements in electrical switch contact structures and one of its objects is to provide a contact having improved stability in circumstances which tend to promote contact vibration.

To overcome contact bounce, to provide sealing and wiping action, and for other reasons, it is common to mount the electrical contacts of fast acting switches on a resilient support. Thus mounted, the contacts yield to one another when they engage such that connection, once made, is maintained and such that they disengage rapidly to minimize arcing. But while this resilience solves some problems it introduces others, an important one of which is to enable the contacts to vibrate. It is possible for vibrating contacts to become damaged and to open momentarily. To avoid this possibility switch designers may design the contacts to have a natural resonant frequency outside the frequency range of any vibration to which the switch might be subjected. Most often it is required to design for a natural resonant frequency above the vibration range by limiting resilience with consequent loss of the advantages of resilient contact mounting.

An alternative is to provide the desired resilience notwithstanding that resonance may occur in the vibration range, and to critic-ally damp or overdamp contact oscillations. It is required, in this alternative, to provide a means for damping. The addition of damping often adds to cost and complexity, reduces reliability and manufacturability.

An object of this invention is to provide an electrical contact structure which includes damping and in which the aforedescribed problems are minimized.

Another object is to provide a contact structure in which damping increases with amplitude of oscillatory movement.

Another object is to provide a contact structure which is suited to mass production even in small and compact relays.

These and other objects and advantages of the invention which will be apparent upon reading of the following specification are realized in part by the provision of a generally U-shaped contact member between whose legs is disposed a generally L-shaped damper spring. The latter is flexed by relative movement of the cont-act legs such that a rubbing or sliding friction action result.

One embodiment of the invention is shown in the accompanying drawings. However, it is to be understood that various modifications of this embodiment and that other embodiments are possible. In the drawings:

FIGURE 1 is a top plan view of a portion of an electromagnetic relay in which the invention is embodied;

FIGURE 2 is a view in side elevation of an electrical contact structure of the kind appearing in FIGURE 1 and which embodies the invention;

FIGURE 3 is a cross-sectional view taken on line 3-3 of FIGURE 1; and

FIGURE 4 is an isometric view of a damper as it appears prior to assembly into an electrical contact structure.

Like reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to FIGURE 1 there is shown the contact assembly of a double-pole double throw relay. Eight connector posts designated by numerals 10, 11, 12, 1'3, 14, 15, 16, and 17, respectively, are secured by insulating headers 18, 19, 20, 21, 22, 23, 24, and 25 to a bottom plate 26. Posts 10 and 14 carry the normally closed contact structure 28 and the normally open contact structure 30 of one switch Whose movable contact structure 32 is mounted on post 12. A similar movable contact structure for the other switch is carried by post 15. The normally open and normally closed contact structures for that switch are carried by posts 13 and 17, respectively. An electromagnetic actuator assembly including coils and an armature and actuating arms which engage and actuate the movable contact structures is disposed above the assembly shown in FIGURE 1. This actuator assembly, which is not shown in the drawings, is secured to bottom plate 26 by supports which are secured in notches 34 in bottom plate 26. The coil of the actuating assembly, not shown, is connected to the other two terminal or connector posts 11 and 16.

Electrical contact 28 is an example of a resilient, undamped contact. Resilience is provided or augmented by the U-shape which extends the length over which the contact can bend. But its resonant frequency is higher than that of the contact structure 30 which, except for the contact engaging portion 36, has its contact member 38 shaped like contact 28. In the embodiment shown, contact member 38 is formed of a strip of the same conductive material from which contact 28 is made but it is made of thinner stock. Thus the resilience of contact member 38 is greater and its natural resonant frequency is lower than that of contact 28.

The normally open contact structure 30 is most readily seen in FIGURES 2 and 3. It comprises, in addition to contact member 38, a generally L-shaped damper 40. In the preferred embodiment, the contact member is substantially U-sh-aped, such as the contact member '38 is shown to be, so that the member is divided into two legs 41 and 42 joined at their inner ends at the bottom 44 of the U. As previously described, the contact engaging portion 36 0f the contact member is for-med. at the outer end of leg 41.

Means are provided for mounting the contact member 30. Advantageously, as shown, this means comprises the combination of connection post 14 and the outer end portion 46 of leg 42 which is wrapped around post 14 and hard soldered to it by a quantity of solder 48. Thus se cured, the contact member is held against rotation relative to post 14 and bottom plate 26.

Means are included for attaching a damper to the contact member 38. In this embodiment that means is a cutaway portion and specificially a hole 50 in leg 42 at a point at its inner end near the bottom 44 of the U.

The damper is a resilient member having a portion which rubs against or slides over some surface that is fixed relative to post 14 or bottom plate 26 whereby the kinetic energy possessed or transmitted by the damper is dissipated by friction as heat. The damper is coupled with the contact member so that movement of the latter produces the rubbing or sliding action. In the embodiment selected for illustration the damper 40 is a generally L- shaped leaf spring. In its unassembled condition it approaches a U-shape as shown in FIGURE 4. It comprises an arm 52 and an arm 54 which join at their inner ends at a juncture or bend 56 in the strip of spring material from which the damper may be formed as shown. A mounting tab 58, integrally formed by cutting away upper and lower sections of the width of the strip material to form the tab 58 which has reduced width to pass through hole 50 and to form shoulder 60 at the outer edge of arm 54. In its assembled position, damper 40 is disposed between the legs 41 and 42 of the contact member with tab 58 extending through hole 50. Tab 58 is drawn through hole 50 until shoulders 60 bear against leg 42 and the tab is then crimped over the edge of the hole and is folded back on itself.

Some structure must be provided against which arm 52 of the damper may rub or slide. It must be positioned so that the juncture 56 of the damper arms engages leg 41 of the contact member and so that the rubbing or sliding action occurs when the contact member moves. A structure is preferred which is fixed relative to the bottom plate 26, which is located between arms 52 and 54 of the damper, and which is far enough away from the connection of the damper and contact member at tab 58 and hole 50 so that the damper is stressed to its L-shape. Thus arranged and trapped, the damper will be biased into engagement at junction 56 with leg 41 and it will be biased into frictional, rubbing or sliding engagement with such structure. Advantageously that structure comprises the connector post and the outer end of the contact member leg which is wrapped around the post. In the preferred form, the outer end 46 of leg 42 is turned inwardly toward leg 41 in wrapping it around post 14 as shown in the drawings. However, it may be turned outwardly if desired.

In operation, when the movable contact 32 is actuated to close the normally open cont-act structure 30 it engages the contact making portion 36. As it continues through its stroke, movable contact 32 will squeeze the contact member 38 forcing leg 41 against its resilience toward post 14. The outer end of damper arm '54 is fixed at shoulders 60 against leg 42. Accordingly, such movement of leg 41 forces the damper spring downwardly. The point of contact X between arm 52 and outer end 46 of leg 42 lies at a greater distance from the apparent center (not shown) about which leg 41 rotates when moved than is point Y at the point at which leg 41 bears against the damper 40. Therefore, as damper 40 is pushed downwardly by leg 41, the arms of the damper are spread apart thereby increasing the pressure at points X and Y. There is relative movement between the damper and the contact member at these points and the friction generated by such movement converts, and dissipates as heat, the kinetic energy imparted to the contact member and the damper by the movable contact.

It is a feature of the invention that greater movement of leg 41 results in greater bias holding the damper to the contact member at points X and Y. The friction at these points increases with bias pressure whereby damping increases as the movable contact completes its stroke.

Although we have shown and described a certain specific embodiment of our invention, we are fully aware that many modifications thereof are possible. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim:

1. An electrical switch contact comprising in combination a mounting post; a contact member comprising a U-shaped strip of conductive material having the outer end of one of its legs wrapped around said mounting post and having its other leg extending past said post to a contact engaging portion at its outer end, said one leg being formed with an opening therethrough at a point between said post and its junction with said other leg; and means for damping movement of said contact member incident to engagement of said contact engaging portion comprising an L-shaped leaf spring having the outer end of one arm secured in said opening and having its other arm biased into engagement with said one leg of said contact member on the side of said post away from said opening, and being biased into engagement at the juncture of said other leg of the contact member.

2. The invention defined in claim 1 in which said outer end of said one leg is wrapped inwardly toward the other leg and around said post.

3. In combination, a contact member comprising a strip of resilient material formed with a pair of legs in a U-shape and means for damping motion of said legs toward and away from one another including an L-shaped leaf spring trapped between said legs and comprising a pair of arms bearing at their juncture against one of said legs, one of said arms being connected to one point on the other of said legs and the other of said arms being biased into slidable engagement with a spaced point on said other of said legs.

4. The invention defined in claim 3 further comprising a mounting post and in which the end portion of said other of said legs encircles the mounting post and said other arm of said leaf spring slidably engages said end portion.

5. The invention defined in claim 4 in which said mounting post and said contact member are electrically interconnected and are formed of conductive material.

6. The invention defined in claim 4 in which said other of said legs is formed with an opening at said one point and the outer end of said one arm extends through said opening and is bent over to form said connection.

References Cited UNITED STATES PATENTS 3,042,773 7/1962 Keller et a1. 335- 3,152,237 10/1964 Richert et a1. 200166 3,260,829 7/1966 Auer 200-166 ROBERT K. SCHAEFER, Primary Examiner.

H. O. JONES, Assistant Examiner. 

3. IN COMBINATION, A CONTACT MEMBER COMPRISING A STRIP OF RESILIENT MATERIAL FORMED WITH A PAIR OF LEGS IN A U-SHAPE AND MEANS FOR DAMPING MOTION OF SAID LEGS TOWARD AND AWAY FROM ONE ANOTHER INCLUDING AN L-SHAPED LEAF SPRING TRAPPED BETWEEN SAID LEGS AND COMPRISING A PAIR OF ARMS BEARING AT THEIR JUNCTURE AGAINST ONE OF SAID LEGS, ONE OF SAID ARMS BEING CONNECTED TO ONE POINT ON THE OTHER OF SAID LEGS AND THE OTHER OF SAID ARMS BEING BIASED INTO SLIDABLE ENGAGEMENT WITH A SPACED POINT ON SAID OTHER OF SAID LEGS. 